Many electronic circuits have a need for limiting current. Voltage regulators and battery chargers are two examples of circuits needing current limit protection, although many other circuits also need current limit protection. Voltage regulators provide a substantially constant voltage over a range of load impedances. However, if the load impedance is relatively small, the voltage regulator must output a very large current to maintain the output voltage. Such a large current can lead to overheating and damage or destruction of the output transistor, as well as nearby components. Frequently it is impractical to provide a heat sink for the voltage regulator due to, for example, space or economic constraints and packaging constraints.
Thus, a need exists for a current limiting circuit for an electronic circuit. A still further need exists for a current limiting circuit that is compatible with and can be fabricated economically with existing semiconductor fabrication techniques.